So she gave you another chance.
The first thing you are going to need to know, brother, is that you don't deserve another chance and she doesn't deserve you. But now that you have this chance, what are you going to do with it? How long will it be before your next argument? The next time she's right up against your face and your eyes are painted red, what will you do about the blood boiling in your fists?
A life of violence sounds exhausting even for you. If you want to free yourself from this vicious cycle, you are going to have to come to terms with some hard truths; that this isn't about her. It isn't even about what she did. This is about the man you see standing in the mirror. This is about his actions. This is about his inability to express himself without needing violence. This is about using fear where love should have flourished.
This is about control.
Somewhere along the line, you accepted the idea that if you can't shout loud enough, then maybe you can hit hard enough. Somewhere along the line you believed that in order for you to be happy, you must be in control of every and any situation. That you are to be obeyed and not considered. That your relationship is better when you are the one making all the decisions.
How has that worked out for you?
Did she get the point after the first three times you hit her? Did she 'change her ways' and start to treat you with 'respect'? If she did (get the point), then you would not have needed to hit her the next three times. Yet, here we are; she is in the other room trying to convince your traumatized son that everything will be okay. He doesn't know whether to believe her or her swollen eye. Last month it was a broken jaw. One day that same boy will have a wife of his own. I pray he grows up to be a better man, not a violent one.
Clearly having all the control is not all that it is cracked up to be; otherwise, you'd be in a happy relationship.
Let go, brother. Let go of control and look around you. No man who has ever had to demand that kind of control has that to thank for a healthy and loving relationship. The opposite is way more common. And no, the opposite of control in this situation is not freedom. She is not a slave. The opposite of control is acceptance.
Accept that her life is not structured around your choices. Accept and show faith in her decisions; even the ones you don't agree with. Showing faith doesn't mean that you can't have an opinion of your own - it just means that she gets the final word with anything that concerns her body and her life. You are not her god, master, or even boss. You are the person she decided to share her life with. Prove to her that she made the right decision.
Prove to her by beginning to work on everything about yourself that threatens her life. Prove to her that you can learn how to be a better communicator. One who prides himself on patience, not power. Prove to her that your value as a man will, from this day, be measured only by the choice of your actions. Prove that she will never need to fear you again.
Prove that love can work without violence.
Have you ever been in a violent relationship?